Corrosion inhibition of carbon steel in hydrochloric acid solution using 5-(4-Pyridyl)-1,3,4-oxadiazole-2-thiol

The inhibiting effect of 5-(4-Pyridyl)-1,3,4-oxadiazole-2-thiol on the corrosion of carbon steel in 1M HCl solution was investigated by electrochemical methods (potentiodynamic polarization and electrochemical impedance spectroscopy) and surface analysis (Raman spectroscopy and SEM-EDX). The polarization curves revealed that 5-(4-Pyridyl)-1,3,4-oxadiazole-2-thiol is able to retard the corrosion process, acting as a mixed-type inhibitor. The inhibition efficiency increases with the inhibitor concentration, reaching a maximum value of 93% at 5mM. EIS measurements showed that the anticorrosive effectiveness of 5-(4-Pyridyl)-1,3,4-oxadiazole-2-thiol is time-dependent. SEM analysis revealed that the metallic surface damage is significantly reduced due to the inhibitor adsorption on carbon steel surface. The presence of the adsorbed organic molecules on the metal was confirmed by the nitrogen and sulfur atoms detected in EDX and Raman spectra. The adsorption of the organic inhibitor on carbon steel surface obeys Langmuir isotherm.